1. Field of the Invention
The present invention relates to a system for analyzing elements of C (carbon), S (sulfur), O (oxygen), N (nitrogen), H (hydrogen) and the like contained in slight amounts, respectively, in a material such as steel, and ceramics and more particularly, to a combustion furnace system that can burn a sample and analyze the gaseous ingredients in an improved manner.
2. Description of Related Art
A method obtained by combining a combustion of a sample in an oxygen gas stream with an infrared absorption scan has been generally used for analyzing quantitatively C, and S contained in steel in slight amounts, respectively. While a method obtained by combining a fusion extracting of a sample in an inert gas with an infrared absorption scan or a thermal conductivity test has also been commonly employed as a method for analyzing quantitatively O, N, and H contained in steel in slight amounts, respectively.
More specifically, the combustion method has a steel sample burned while feeding oxygen gas into a heating furnace and the resultant combustion gas, containing CO/CO2 and SO2 produced at that time, is analyzed by a nondispersive infrared analyzer (NDIR). The fusion extraction method has a graphite crucible containing a sample such as steel disposed in a heating furnace, the sample is heated and fused while feeding an inert gas to the combustion chamber, and the CO2 produced at that time is analyzed by a NDIR, while N2 and H2 are analyzed by a thermal conductivity method.
In both of the method s described above, a lower limit of detection for an element in the sample is about 1 wt ppm (although 0.1 wt ppm is possible with respect to H). However, there is a demand for new materials such as metals and ceramics having a higher purity to be employed in recent years, so that the elements, as described above as impurities must exhibit a lower concentration level.
Under these circumstances, the sensitivity of the testing procedures have become insufficient in conventional analyzers as described above, and as a result, a precise determination cannot be effected. In addition, there is also a problem of a false or blank value due to possible contamination of a graphite crucible, so that an accurate determination in the region of very slight amounts of impurities becomes difficult.
Although there is known an ICP-MS method and the like as one type of analyzing method for analyzing steel and the like by the use of a mass spectrometer, it is difficult to realize a measurement with sufficiently high sensitivity, because a large amount of a major component (for example, Fe) of the sample material enters the mass spectrometer, so that the potential excellent resolving power and excellent sensitivity in the order of a ppb which could be derived from a mass spectrometer cannot be easily achieved.
Other examples of combustion furnaces for burning a sample to be analyzed can be found in U.S. Pat. No. 5,110,554, U.S. Pat. No. 3,936,587, U.S. Pat. No. 4,087,249. U.S. Pat. No. 4,234,541 and U.S. Pat. No. 5,236,353.
There is still a desire in the prior art to optimize the ability to measure very minute amounts of elements in a sample in an economical and efficient manner.
An object of the present invention is to provide a system for analyzing elements contained in a sample (hereinafter referred to simply and optionally as an xe2x80x9celement analyzerxe2x80x9d) by which elements of C, S, O, N, H and the like which may be contained in very slight amounts, respectively, in a sample material such as steel, ceramics and the like can be quantitatively analyzed with high sensitivity.
In order to attain the above described object, the element analyzer according to a first embodiment is constituted so that a sample is burned up while feeding oxygen gas into a high-frequency heating furnace or an electric resistance furnace, and the gas produced at that occasion is introduced to a mass spectrometer, thereby to analyze quantitatively at least any one element of C, S, and N.
An element analyzer according to a second embodiment uses a graphite crucible containing a sample. The crucible is placed into an impulse furnace, and the sample is heated and fused while feeding an inert gas into the furnace. The resultant gas is extracted and introduced into a mass spectrometer, thereby to analyze quantitatively at least one element, such as O, N, and H that may be contained in the sample.
Furthermore, an element analyzer according to a third embodiment has the sample heated while feeding a hydrogen gas to an electric resistance furnace, and the gas produced at that occasion is introduced into a mass spectrometer, thereby to analyze quantitatively at least any one of C, S, and N.
In any of the above described element analyzers, the desired elements to be measured can be analyzed quantitatively with high sensitivity. The mass spectrometer can concentrate its excellent resolving power at specific components to be measured thereby to achieve a measurement with higher sensitivity, over that of the prior art, as a result of removal of oxidized dust by means of a dust filter, removal of water vapor (moisture) by means of a dehumidifier, and oxidation of CO into CO2 by means of an oxidizing device.
In any of the above described element analyzers, it may be alternately arranged so that a gas initially produced in a furnace is again supplied to the furnace through a re-circulating passageway before the final combustion or extraction of the sample, and the above described gas is then supplied to the mass spectrometer after completing the combustion or extraction. According to such an arrangement, stable measured results can be obtained in a single procedure of testing.
An element analyzer according to a fourth embodiment is constituted in such a manner that a laser beam of an appropriate intensity is irradiated upon a metal sample, which is disposed in an irradiation cell, to which is selectively introduced oxygen gas or an inert gas, and a gas produced at that occasion is then introduced to a mass spectrometer to analyze quantitatively at least any one of carbon, sulfur, nitrogen, and hydrogen contained in the metal sample.
Moreover, an element analyzer according to a fifth embodiment has a laser beam irradiating a metal sample which has been disposed in an irradiation cell to which is introduced oxygen gas, and a gas produced at that occasion is introduced to a mass spectrometer, thereby to analyze quantitatively either of carbon, and sulfur contained in the metal sample.
Still further, an element analyzer according to a sixth embodiment is constituted so that a laser beam is irradiated upon a metal sample disposed in an irradiation cell to which is introduced an inert gas, and a gas produced at that occasion is introduced to a mass spectrometer, thereby to analyze quantitatively either of nitrogen and hydrogen contained in the metal sample.
Yet further, an element analyzer according to a seventh embodiment is constituted so that a laser beam is irradiated upon a metal sample disposed in an irradiation cell to which are introduced hydrogen gas and an inert gas at a predetermined ratio, and a resultant gas produced at that occasion is introduced to a mass spectrometer, thereby to analyze quantitatively at least any one of carbon, sulfur, and nitrogen contained in the metal sample.
In the above described element analyzers according to the fourth to the seventh embodiments, desired elements can be analyzed quantitatively with high sensitivity. The mass spectrometer can concentrate its excellent resolving power at components to be measured and thereby achieve measurement with higher sensitivity as a result of removal of oxidized dust by means of a dust filter, and removal of water vapor (moisture) by means of a dehumidifier.
An element analyzer according to an eighth embodiment is constituted so that either one of an inert gas and an oxygen gas can be supplied to an extracting cell around which has been wound a high-frequency coil. While the high-frequency coil is energized, the metal sample is maintained in position inside the extracting cell by means of high-frequency levitation, at the same time, the sample is heated and fused, and the gas produced at that occasion is conveyed and carried by the inert gas or the oxygen gas to the mass spectrometer, thereby to analyze quantitatively therein at least one of carbon, sulfur, nitrogen, and hydrogen contained in the metal sample.
Furthermore, the element analyzer according to a ninth embodiment is constituted so that oxygen gas is supplied to an extracting cell around which has been wound a high-frequency coil. When the high-frequency coil is energized, the metal sample is maintained at an elevated position inside the extracting cell by means of high-frequency levitation, at the same time, the sample is heated and fused, and the gas produced at that occasion is conveyed and fed to the mass spectrometer by means of the oxygen gas, thereby to analyze quantitatively therein at least one of carbon, sulfur, and nitrogen contained in the metal sample.
In addition, it may be arranged in the above described eighth and the ninth embodiments that the high-frequency coil is moved vertically along the longitudinal direction of the extracting cell.
In the above described element analyzers according to the eighth and the ninth embodiments, desired elements can be analyzed quantitatively with high sensitivity. The mass spectrometer can concentrate its excellent resolving power at components to be measured to achieve measurement with higher sensitivity as a result of removal of. oxidized dust by means of a dust filter and removal of water vapor (moisture) by means of a dehumidifier.